1. Field of the Invention
The present invention is directed to a rotary dry shaver, and more particularly to a rotary dry shaver having a floating outer shearing foil capable of being depressed when pressed against the skin of a user.
2. Description of the Prior Art
In a typical rotary dry shaver, as shown in FIGS. 8A, an inner cutter holder 140 is provided to carry a plurality of inner blades 141 (although only one of which is shown for simplicity) and is driven by a rotary shaft 112 to rotate about an axis thereof with the inner blades 141 kept in shearing engagement with a perforated outer foil 150 which is supported at its periphery to a head frame 130. Since the outer shearing foil 150 is required to be thin in order to enable a close shaving, the outer shearing foil 150 is likely to flex when pressed against the skin of a user during the shaving. In this type of the dry shaver, a problem is encountered when the outer shearing foil 150 is depressed at its center portion, as shown in FIG. 8B. That is, in the absence of such deformation of the foil 150, the whole inner blades 141 can be placed in constant shearing engagement with the foil 150 over the entire length of the blade 141, as shown in FIG. 8A. However, as the foil 150 is depressed to thereby lower a corresponding end portion of the inner blade 141, the other end portion is spaced from the foil 150 to leave a gap therebetween, which results in worsening cut sharpness with attendant noise increase and even in failing to continue the shaving. To avoid the problem, it has been proposed in a prior art rotary dry shaver, as disclosed U.S. Pat. No. 3,636,626 to use a pin which extends from a like drive shaft for supporting the center portion of the outer shearing foil. The pin is connected through a spring to the drive shaft so as to support the foil with a suitable spring bias. Thus, the center portion of the foil is urged outwardly to resist deformation which would otherwise cause the above problem. In this prior rotary dry shaver, the other portion of the foil is held in shearing engagement with inner blades which are carried on cutter holders. The cutter holders are supported to the drive shaft through springs in such a manner that the other portion of the outer shearing foil is floatingly supported by means of those springs. However, with this structure in which the outer foil is supported on the inner cutter holders which in turn supported through the springs to the drive shaft, there arises another problem in that when the outer foil is depressed against the skin of a user, the depression force acts firstly and directly on the engagement between the outer foil and the corresponding inner blades to thereby increase contact pressure therebetween. Such variation of the contact pressure is detrimental to the cut sharpness and therefore the contact pressure should be maintained at a desired level without being influenced by the depression of the outer shearing foil.